Electrooptical system



Oct. 8, 1929. D. K. GANNETT 1,730,416

BLECTROOPTICAL SYSTEM Filed Aug. lO, 1928 2 Sheets-Sheet l Oct., 8,1929, D. K. GANNETT 1,730,415

ELECTROOPTICAL SYSTEM Filed Aug. 10;. 1928 2 Sheets--Sheefl 2 I I l RYIL il /N VEN m f? B DAM-@HTH (24M/V577' Patented Oct. 8, 1929 UNITEDSTATES PATENT OFFICE D'ANFORTH K. GANNETT, 0F JACKSON HEIGHTS, NEW YORK,ASSIGNOR '10 AMERICAN TELEPHONE AND TELEGRAPI-I COMPANY, A CORPORATIONOF NEW YORK ELEGTROOIETIGALl SYSTEM Application filed August 10, 1928.

This invention relates to electric-optical systems and particularly toan electro-optical image producing system in which one portion of theimage is produced in finer detail than another. i

An object of the invention is to automatically control the detail withwhich a given portion of the image is produced.

Another object of the invention is to scan a portion of a field of viewin detail to produce an image current forL controlling the production ofan image and automaticallyV varying the portion of the field of viewloeing scanned.

`Still another object ofthe invention is to automatically vary theportion of the image which is produced in fine detail to correspond withthe line of vision of the observer.

There is disclosed in Patent No. 1,624,918 lgranted to O. B. Blackwelland Joseph Herman, April 19, 1927, a television System in which oneportion of the image is produced in finer detail than another portion. Amanually operable device is provided for varying the portion of theimage which is produced in fine detail. This device may be adjusted bythe observer so that the portion of the image toward which his vision isdin rected is at all times produced in finer detail than the otherportions of the image.

Tn accordance with an embodiment of the present invention shown anddescribed herein, the detail withV which a portion of the image isproduced is controlled automatically. For this purpose there areprovided two banks of long light-sensitive cells, the cells of one bankbeing arranged horizontally and the cells of the other bank beingvertical and positioned in front or in back of the first bank. of t-heeye of an observer is focussed on the banks of light-sensitive cells.The cells of each bank are connected to a common circuit zontal positionof the-image. The potential An image of the pupil in such a manner thatthe potential drop Serial No. 298,758.

variations across these circuits are employed to control the amplitudeof the carrier current'from two dierent sources. These carrier currentssimultaneously control the position of two lenses, one at thetransmitting station and one at the receiving station for controllingthe position of the portion of the object which is scanned in finedetail and the position of the corresponding portion of the image whichis produced in fine detail.

In another embodiment of the invention a beam of light directed onto theeye of the observer is reflected to the banks of lightsensitive cells.This reflected light impinges on different portions of the banks oflight-sensitive cells in accordance with the movement of the eye forcorrespondingly varying the potential set up across a circuit connectedto each bank of light-sensitive elements.

The invention will be readily understood by referring to the followingdescription and the accompanying drawing in which lFigure 1 is adiagrammatic showing of ya traismitting station of a television system;an Fig. 2 shows diagrammatically a receiving station of the televisionsystem.

Referring to Fig. 1 of the drawing, light reflected from the object 10is passed through a movable lens 11 and thence through the analyzer orscanning mechanism 12. The light which passes through the scanning`mechanism is focussed on the light sensitive cell 13 by the lens 14. Thescanning mechanism 12 is driven by a suitable driving device such as theSynchronous motor 14 and comprises two slotted discs which rotate insuch a manner that the opening formed by the intersection of the slotsdescribes a spiral. The scanning mechanism is described in greaterdetail in the patent to Blackwell and Herman referred to hereinbefore.By means of this scanning mechanism, the object 10 or a portion thereofis scanned along a spiral line. The portion of the object near thecenter of the spiral is scanned more slowly and hence in greater detailthan the portions away from the center. The scanning mechay creases withthe distance from the center of the spiral.

The quantity of light falling on the light sensitive cell 13 determinesa corresponding current to the input ofthe modulator 15 which issupplied with current of frequency f1 from the current source 16.Accordingly` this current of frequency f1 is modulated Vto corre` spendto the intensity of the light received from the'successively scannedelement areas of the object 10. The modulated current passes through thefilter 17 and over the line 18 to the receiving station shown in Fig. 2.The power current for the synchronous motor 14 may be an alternatingcurrent of 60 cycles per second. A current of frequencyk f2 is suppliedfrom the source 21 to the modulator 2O 1 and is there modulated by thealternating current supplied from the source 19. The out.n put of themodulator 20 goes through the filter 22 and is also put on the line 18along` with the current of frequency f1 modulated according to thelight'actuating the light sensitive cell 13.

At the receiving station shown in Fig. 2 the modulated currents of basicfrequencies f1 and f2 go, respectively, to the appropriately designedfilters 23 and 24 and thence respectively to detectors 25 and 26 Whoseoutput circuits carry currents corresponding to `the modulated currentsproduced at the transmitting station. The amplifier 27 receives currentofthe same Afretuiency as that supplied from the source 19 to thesynchronous motor 14and thus the amplified output current from i A theamplifier 27 drives the synchronous motor 28 at the same speed as themotor 14 is driven, y

and the scanning device 29 at the same speed as the scanning device 12.The scanning device 29 is a duplicate of the device 12,V having an'opening formed by the intersection of two slot-s, and this openingldescribes aY spiral'course rapidly repeated in synchronism with thespiral traversed at the sending end. Light from a determinate portion ofthe source 30 goes through the light valve 31 to the opening in thedevice 29 and is tion.

focussed by the lens 32 in a small spot on the screen 33. This spotdescribes a spiral and at 'each point of this spiral the degree ofillumination is determined by the light valve 31 'in correspondence withthe degree of illumination of a corresponding elemental area of theobject 10 at the transmitting sta- Since the spirals are repeated 16 ormoretimes per second, an observer looking at the screen 33 sees an imageof the object and, if

if there is motion in the object, he sees the' mot-ion.

When a person views an object or objects having motion, he ordinarilyiixes his attention and directs his gaze on a small central region ofhis entire field of View and IGCGVGS observer is focussed 4on two-banksof `long light sensitive cells, the Vcells 34 of one bank being arrangedhorizontally and the cells 35 of the other bank being Vertical and infront of the first bank.4 The port-ions of the banks of light sensitivecells surrounding the image -.of the pupil of the eye formed thereon areilluminated by light reflected from the portion of the eye surroundingthe pupil and from. the face of the observer. Asthe observer moves hiseyes so as to observe dilferentportions of the image formed on thescreen 33, the image of the pupil of one of his eyes formed on the banksof light sensitive cells 34 and 35 correspondingly changes in position.The light tone value of the pupil of the eye corresponds to .black whilethe surrounding portions of the eye andthe face are of relatively lighttone value. The light sensitive cells are preferably so arranged thatthe image of the pupil of the eye covers a portion of one of thevertical cells and one of the horizontal cells. The impedance of thecells on which the image of the pupil of the eye is focussed is greaterthan the impedance of the remaining cells and the current through thefirst mention-ed cells is correspondingly decreased. One terminal ofeach of the horizontally arranged cells 34 is connected to one terminalof battery 36, while y the other terminalof each cell is connected v.toa terminal of one vof the resistance elements 37 which are connected inseries. end terminal o'fthegroup of resistance elements is. connected to`the other terminal of battery 36. In a similar manner one terminalofeach 1 of the vertical cells is connected to one terminal of thebattery 38, while the other terminal of each cell is connected to aterminal of one of the groups of series connected resistance elements39. One end terminal of this y source of current of frequency f3 isconnected to the primary winding of transformer 41.

The anode circuit of modulator tube 42 is connected to the primarywinding vof transformer 43, the secondary win-ding of which is connectedto the band pass lilter 44. The end terminal of the group of resistanceelements 39 is similarly connecte-d through bias- The anode circuit ofmodulator tube 47 is i coupled through transformer 48 to the band passfilter 49.

It is apparent from an observation of the circuit arrangement, that wheneach of the similar cells 34 and 35 is equally excited by light, theinternal resistances of the cells are c equal. lhen an image of thepupil of the eye is formed on several of the'cells, the resistance ofeach of these cells increases and the potential differences across thegroup of resistance elements 37 and across the group of resistanceelements 39 correspondingly decrease. The decrease in potential dropacross the group of resistance elements 37 is greatest when the image isformed on the upper light sensitive cell as viewed in the figure andleast when formed on the lowest cell of the group. Similarly, thedecrease in voltage across the group of resistance elements 39 iSgreatest when the image of the pupil of the eye is formed on the celltoward the right as viewed in the ligure. The potential applied to thecontrol electrode of the modulator vacuum tube 42 is thus determined inaccordance with the vertical position of the image of the pupil of theeye, the higher the image the smaller the potential applied to thecontrol electrode. In a similar manner the potential applied to thecontrol electrode of the modulator vacuum tube 47 decreases as the imageof the pupil of the eye moves to the right as viewed in the figure.Accordingly the current of frequency leaving the filter 44 has anamplitude which varies in accordance with the vertical position of theimage of the pupil of the eye, while the current of frequency f4 leavingthe filter 49 has an amplitude which varies in accordance with thehorizontal position of the image.

The current leaving the filter 44 is detected by the detector 50, theuni-directional output current of which goes to the movable coil 51which is in the magnetic field produced by the direct current in thewinding 52. The arm 53 carried by the movable coil 5l is adapted toshift the lens 32 in a vertical direction as viewed in the ligure. Thecurrent leaving the filter 49 after being detected by the detector 54goes through the movable coil 55 which is in the magnetic eld producedby the direct current in winding 56. The arm 57 carried by the coil 55is adapted to control the movement of the lens 32 in a directionperpendicular to the plane of the drawing, the coil 55 being turned tofacilitate its showing in the diagram.

The current-s of frequencies f., and f4 leaving the filters 44 and 49,respectively, are also transmitted over line 18 to the transmittingstation Where they are separated by filters 58 and 59 and then go to thedetectors 60 and 61, respectively. The uni-directional output cur rentsfrom these detectors correspond to the output currents of detectors 50and 54, respectively. These output currents act upon the coils 62 and63, respectively, to control the position of the lens l1 in accordancewith the position of the lens 32. v

As the observer directs his attention to different portions of the imageformed on the screen 33, the position of t-he image of the pupil of hiseye formed on the banks of light sensitive cells 34 and 35 shiftscorrespondingly. As a result the currents leaving the filters 44 and 49vary correspondingly and determine the position of the lenses 11 and 32.The positions of these lenses in turn determine the portion of theobject 10, which is scanned in fine detail and the corresponding portionof the image formed in tinedetail on the screen 33, this portion of theimage being the one to which the attention of the observer is directed.

Instead of focussing an image of the pupil of the eye of the observer onthe banks of light sensitive cells, a small beam of light may bereflected from the eyeball of the observer onto the banks of lightsensitive cells. Since the eyeball is not perfectly spherical in shapethe position of the beam as it reaches the banks of light cells variesin accordance with the direction in which the observer is looking.

The range of frequency components of the current transmitted forproducing the image is limited by the transmission characteristics ofthe transmission channel. lf, instead Vof scanning a portion of thefield of view in fine detail and another portion in less detail as inthe system disclosed herein, the entire field of view be scanned in linedetail, it would be necessary to transmit an image current having arelatively wide range of frequency components or otherwise to decreasethe size of the image produced. If it be desired to produce'a largeimage of a field of view which is scanned uniformly by transmitting theimage current over a channel capable of transmit-- ting only arelatively narrow band of frequencies,'the image will be produced inpoor detail. It is thus apparent that the frequency range which can betransmitted over a chanautomatically varying the portion of the field ofview being scanned.

. 2. The method of producing an image electro-optically, which comprisesscanning` a portion of a lield of view in fine detail, scanning anotherportion oit the field of view in less detail, producing an image currentas the result of said scanning, utilizing said image current to controlthe production of an image in accordance with said scanning, andautomatically varying the portion of the field of' view which is beingscanned in fine detail.

3. An electro-optical image producing system, comprising means forscanning a field of View to produce an image current, said means beingadapted for scanning one portion of the field of view in finer detailthan another portion. thereof, means responsive to said image currentfor producing an image of said field of view, the detail of differentportions of which is controlled 'in accordance with said scanning, andmeans for automatically varying the portion ot the field ot view whichis scanned in fine detail as the observer directs his vision towarddifferent portions of the image.

4. An apparatus for controlling the position of an element in accordancewith the movement of the eye ot' an observer which comprises a group oflight sensitive cells, and means for varying the impedance of at leastone of said cells in accordance with the movement of the eye of saidobserver.

5. An apparatus for controlling the position of an element in accordancewith the movement of the eye of an observer which comprises an electriccircuit, a plurality of Alight sensitive cells connected to saidcircuit, and means including said light sensitive cells for controllingthe voltage drop across at least a portion of said electric circuit inaccordance with the movement of the eye of said observer.

6. An apparatus for controlling the position of an element in accordancewith thel movement of the eye of an observer which comprises a bank oflight sensitive cells, and means forcausing light reflected from the eyeof the observer to reach said bank of' light sensitive cells forcontrolling the impedance of different cells in accordance with themovement of the eye of said observer.

7. In an electro-optical image producing system, means for scanning afield of view to produce an image current, means for utilizing saidimage currentfor producing an image of said field of view, and means forshifting the,field of view being scanned in response to the movement ofthe eye of an observer.

8. In an electro-optical image producing system, means for scanning afield of view to produce an image current, means for utilizing saidimage current for producing an image of said field ot' view on a screen,and

`the position of said device.

means for shifting the field of view being scanned in accordance withthe portion of the screen toward which the observer directs his of saidcells tor controlling the position of movable element over a range ofpositions bef tween fixed limits. y

10. In an electro-optical system, two banks of long light sensitivecells, the cells of one bank being positioned so that their longitudinalaxes form an angle with the longitudinal axes of the cells of the otherbank, two groups of series connected resistance elements, one groupbeing associated with eachY bank of light sensitive cells, an electricalconnection from each light sensitive cell toa terminal of a differentresistance element, means for directing light from the eye of anobserver onto said banks or" light sensitive cells for controlling thepotential drops across said groups of resistance elements, a deviceWhich is to be moved in accordance with the movenient of the eye of saidobserver, and means responsive to the potential drops across said groupsof resistance elements for controlling In testimony whereof, I havesigned my name to this specification this 9th day of August, 1928.

DANFORTH K. GANNETT.

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